The present invention relates to hydroelectric power installations which utilize turbine generator sets to produce electrical power from the pressure head available at a dam. The invention is particularly advantageous for constructing hydroelectric power installations where the pressure head is generally low and at existing water control facilities which have low level discharge gates and tunnels.
The construction of a hydroelectric installation inherently requires the placement of a turbine generator set and draft tube assembly in a location that is normally well below head water level. Generally a contractor builds a power house downstream of the dam at the site of the proposed installation and then assembles the turbine generator set in place by bringing the individual turbine and generator components into their operating positions. To maintain the water pressure head at the downstream location, the discharge tunnel under the dam must be fitted with a steel liner that will support the water pressure and eliminate water losses through the fissures or permeable soils in the tunnel. The liner in turn must receive a protective interior coating for long-term preservation.
Such construction techniques obviously entail the time and expense of building a power house and pressurized water delivery conduit, but allow a large turbine generator set to be put in place. Servicing of such a generator set later presents access problems, and may require significant disassembly. Delays in repair under these circumstances can be lengthy and may require that substitute power be obtained from an alternative source during the shutdown period.
Also, the size of large turbine generator sets may be so great that transportation of the assemblies is a problem. Additionally, with large turbine generator sets, the total weight may be so great that handling can not be accomplished on site without breaking the sets down into subassemblies. Lifting an assembly into position may be impossible without designing and building new support structures to set up and operate a crane.
An alternative technique for constructing power installations by assembling smaller generator sets above the water level and then submerging the sets upstream of the dam has significant appeal from a cost and efficiency standpoint. First of all, the components and castings for smaller turbine generators can be more readily obtained from a larger number of suppliers, which include machine shops and foundries. Larger components may have limited distribution or may not be available at all except by special order from only a limited number of turbine generator manufacturers with long lead times and extended completion dates. An earlier completion date results in a faster return on the investment through the power generated.
The smaller turbine generator sets also offer the advantage that they can be installed in a smaller structure since, for a given water passageway shape and installed capacity, the length of the turbine is generally proportional to the turbine runner diameter. Smaller turbine generators, therefore, decrease the cost of the peripheral support structures.
Smaller turbine sets also provide a higher specific output per unit weight. Thus, lifting cranes and similar support equipment can be scaled down where an array of smaller turbine generator sets are used in place of a single or lesser number of large turbine generator sets producing the same installed power.
Small turbine generator sets are also easily transported by rail or truck while in some cases large turbine generator assemblies must be constructed at the site because their size or weight exceeds the capacity of lifting cranes, vehicles and roads or access bridges.
A hydroelectric power installation utilizing an array of smaller turbine generator sets also produces long-term economies since individual or sub-groups of the generators can be removed from service for repair or replacement without totally shutting down the power generating facility.
It is accordingly a general object of the present invention to provide small, compact, light weight turbine generator sets which can be readily transported to a hydroelectric power installation and be assembled above the water level and then be lowered by conventional equipment into a submerged, upstream operating position for power generation.